Help: What can it be??

So here is the thing...when I am at a red light and press on the gas peddle about half way the car is good then when I get to 30mph the car starts to sputter until I hit about 50mph...then it will smooth out, but if I have the gas peddle down half way then floor it, it will stop sputtering...and I can get it up to 70 smooth.... but if I slow... to about 55mph and ease back on the peddle it will sputter. Any ideas??? 98 Cutlass V6 3100 over 150K miles

side note: the check engine light came on it said it detected a misfire in cylinder 1 then I cleared out the code has not come back on yet

Sounds like you" sputter" may be related to the code a misfire in #1 cyl. bad plug, wire, coil, or injector, all possibilities.

Is there any way to narrow it down, without just changing everything?
Any good test that i can preform

If it has not returned and there is no noticeable misfire, wait and see. If it still does it start with plugs and wires if they are old.